Nutrient Role in Bioenergetics Chapter 4 Part 2

Bioenergetics-Glycolysis  Carbohydrates primary function  Energy for cellular work.  Breakdown of 1 mole of glucose liberates 686 kCal of energy. 233 kCal (34%) usable The remainder dissipated as heat.

Bioenergetics  Glucose Degradation - glycolysis  Occurs in two stages: 1. Anaerobic: Glucose breaks down relatively rapidly to 2 molecules of pyruvate → lactate 2. Aerobic: Pyruvate degrades further to carbon dioxide and water.

Glycolysis Occurs in cytoplasm  Enzymes ATP required as phosphate donor  Glucose → glucose-6-phosphate ATP required as phosphate donor  Fructose 6-phosphate

Glycogenolysis Catabolism of muscle glycogen  Glycogen phosphorylase Glucose-6-phosphate  Epinephrine

Glycolysis

Hydrogen ions released during glycolysis  NAD → NADH  Additional 5 ATP molecules (ETC)

Bioenergetics Aerobic glycolysis  C 3 H 4 O 3 – pyruvic acid  Rest, light to moderate levels  Hydrogen + Oxygen → H 2 O

Bioenergetics  Anaerobic  NAD availability  Lactate formation  C 3 H 4 O 3 + 2H + → C 3 H 6 O 3  Pyruvic Lactic  Acid Acid

Bioenergetics  Aerobic  C 3 H 4 O 3 + 2H +  C 3 H 6 O 3  Pyruvic Lactic  Acid Acid

The Cori Cycle: Lactate As a Fuel Source Fig 4.16

Bioenergetics Citric Acid Cycle (Krebs cycle).  The second stage of carbohydrate breakdown  Pyruvate converts to acetyl-CoA, degrades  Carbon dioxide and hydrogen atoms- mitochondria  Most important function  Generate H ions for Electron Transport Chain (ETC)

Bioenergetics

 Stored fat  Largest source of potential energy.  Supplies fatty acid molecules  Energy sources for fat catabolism include: Triacylglycerol Muscle fiber - stored Lipoprotein complexes - circulating Free fatty acids - circulating

Bioenergetics Energy metabolism – lipolysis  FFA + glycerol Form intracellular triglycerides Bind with intramuscular proteins

Bioenergetics  Adenosine 3’,5’-cyclic monophosphate  Cyclic AMP -  Hormonal effects  Epinephrine, norepinephrine, glucagon, and growth hormone

Bioenergetics

 Glycerol Provides carbon skeletons for glucose synthesis  Fatty acids Beta (ß)-oxidation converts a free fatty acid to multiple acetyl-CoA molecules. Hydrogen ions oxidized through the respiratory chain.

Bioenergetics

Fats in CHO Flame FA breakdown requires CHO breakdown  Intermediates of citric acid cycle Oxaloacetate (pyruvate) Malate

Bioenergetics  Lipogenesis  The formation of fat  Cytoplasm of liver cells  Excess glucose or protein not metabolized  Converted into stored triacylglycerol  The lipogenic process requires:  ATP energy  B vitamins  Biotin, niacin, and pantothenic acid.

Bioenergetics  Protein  Energy substrate  Endurance activities  Heavy trainings.  Deamination: Nitrogen removed from amino acid  Pyruvate  FA synthesis

Bioenergetics  Protein  Catabolism facilitates water loss.  The amine group of protein breakdown must be eliminated.  “O bligatory ” water as the waste products of protein catabolism leave the body dissolved in fluid (urine).

Bioenergetics

 Metabolic Mill  The citric acid cycle  Link  Food energy and the chemical energy of ATP.  Intermediates  Mitochondrial membrane into the cytosol to synthesize bionutrients.

Metabolic Mill